Self-locking nut



April 13, 1965 J. A. M LEAN m, ETAL 3,177,914

SELF-LOCKING NUT Filed April 5, 1965 INVENTORS JOHN A. MAC LEANlII-DECEASED BY JOY 0. MAC LEANMQIDDMINISTRATOR JOHN A. MAC LEAN,JI2. By W W/um, fi/zwm 6W days.

United States Patent h Ofilice Patented Apr. 13, 1965 This invention relates to self-locking nuts, and more particularly to hexagonal self-locking nuts usable from either end and which are normally freespinning on a coacting fastener element until the seating position is reached and then may be locked firmly without material weakening of the nut structure or the engaged threads.

One of the objects of this invention is to provide a normally free spinning nut structure which locks as a result of distortion when seated, and which has seating surfaces constructed and disposed to effect a definite limitation of nut distortion to that required for locking.

As another object, this invention comprehends the pro vision of a self-locking hexagonal nut wherein the end surfaces are grooved at positions aligned with the midregions of opposed flat side surfaces, thereby to provide localized regions for fiexure to effect locking, while retaining full nut height at the corners between the side faces for wrench engagement.

Another object of the invention is to provide a selfloclsing hexagonal nut which, although having areas of reduced section for flexure to obtain locking action, has sufficient threads to afford strength.

This invention has within its purview the provision of a hexagonal self-locking nut wherein the structure, part relationships and proportions are correlated to establish in the nut such factors as ability to develop, in addition to a strong self-locking feature, the ability to accomplish full bolt tension, flexibility forlocking action within the range of reasonable wrench torque, full length corners and limited external side distortion to provide good wrench holding characteristics. e

Other objects and advantages of the invention will be apparent from the following description taken in con junction with the accompanying drawings in which:

FIG. 1 is a top plan view of a self-locking nut embody ing a preferred form of this invention;

FIGS. 2 and 3 are side elevational views of the self locking nut shownin FIGURE 1, wherein the views are taken from positions 99 apart; a p

F194 is a side sectional view taken substantially on a line t4 and in the direction of the arrows, as indicated in FIG. 1; and

PEG. 5 is a fragmentary side elevational view of a nut of the type shown in FIG. 1 shown in its tightened and locked position relative to a stud which projects from a part having a substantially fiat seating surface.

the exemplary embodiment of this invention which is depicted in the accompanying drawings for illustrative purposes, a hexagonal self-locking nut t has a body l2 22 are recesses 29 and 3%, which recesses are concavely curved, and in the particular form disclosed, are arcuate with centers 32 and 33 located exterior to the opposite ends of the nut body. Opposite end surfaces of the nut are substantially alike, so that the nut is-usable from either end. Also, considering a central axially disposed .thatthe recesses 29 plane extending longitudinally of the recesses2 9 and 30 and passing through the centers 32 and 33 of the recesses, as well as the center of the threaded opening 13 as a reference, the end surfaces 14 and 15 have portions on opposite sides of the plane which are substantially symmetrical with respect to one another. These end surfaces include substantially fiat end surface portions 34, 35, 36 and 37. The end surface portions 34 and 35 extend outwardly from the opposite sides of the recess 29 and from the central threaded opening, while the end surface por- .tions 36 and 3'7 extend outwardly from opposite sides of the recess 35? and the central threaded opening. In their extent outwardly from the opposite sides of the recesses 29 and St in directions lateral to the recesses, the end one another in obtuse angular relationship, and so that they form an angle with respect to one another which is somewhat less than a straight angle. In F1613, the deviation of the angularity of the end surface portion 37 from a straight angle is designated by the angle a. In the illustrated structure, the angle a, in various sizes of nuts, is between 4 and 6, so that the angularity between the fiat end surface portions at each end of the nut is between 168 and 172. p

The end surface portions 34, 35, 36 and 37' each being flatand being angularly disposed on opposite sides of each recess and end surface, it may be readily understood that opposite mid-regions of the flat end surfaceportions extend outwardly toward opposed corners 23 and 25 of the nut body, whereby those corner regions of the nut body are thicker than other portions thereof, so that initial contact between the nut body and an opposed flat'surface,

such as 30 in FIG. 5. when the nut is threaded onto a ,mating part, such as a stud 39, is at the opposed corner regions of the nut. I

it is to be understood that nuts made in accordance with this invention shall be made of metal, such as steel be observed that a limit of the'locking distortion is reached when the flat end surface portions of one end surface of the nut bottom against an opposing flat surface, as shown in FIG. 5.

which limit the thickness of the nut body therebetween afford a iiexure region for the nut body which is between the angularly disposed flat surface portions of the ends, and at which the nut body flexes when tightened against an opposing surface. Additionally, it is to be observed and fill have a maximum width b which is narrower than the diameter of the central threaded opening 125. Since the flat surface portions of the end surfaces of the nut body extend outwardly from the opposite sides of the recesses, and bottom against an opposin surface, there can be no further fiexure of the nut body beyond the point at which the fiat surface portions bottom, which furthervfiexure would tend to lift the corners of the nut away from the flat surface, and fur exist. 7

It will be readily understood that nuts of the type herein disclosed spin freely and without any locking action until the nut makes'its initial contact with an opposing surface. in flexing, as a result of the engagement of the an ularl dis osed flat end surface ortions In this respect, it is noter worthy that the opposed and aligned recesses 29 and 3t 'nut body or materiallyweakenthe threads or thread engagement between the nut and a bolt or stud at the bottom end region of the nut which would, in turn, limit the bolt tension which could be developed by tightening the nut.

In addition to the foregoing, there are certain additional structural and proportional characteristics of the disclosed nut which. contribute to its effectiveness and efficiency as compared to those which have been known before. For example, by having the aligned and opposed recesses 29 and 30 extend between the mid-regions of opposedside faces, all corners of the nut body are left intact for their full lengths to provide improved Wrench engagement, and to minimize the possibility of slippage of a wrench on the nut when it is tightened, and particularly when it becomes somewhat distorted as a result of its locking flexure. The angularity of the flat end surface portions of the nut is selected not only to produce effective locking action on bolts made within commercial limits, but also to obtain a full contact been each end surface portion and the opposing flat surface and'also limit the produceable taper resulting from flexure which could limit engagement with a wrench.

body thickness T to the minimum distance D between the recesses 29 and 30 is desirably kept between approximately 2% and 2 1 in different sizes of nuts. 7 a

From the foregoing description and reference to the accompanying drawings, it may be understood that this invention provides a double ended or two-way self-locking nut which spins freely until it makes contact with an opposing surface and wherein the structure, part relationships and proportions are correlated to establish in the nut such factors as ability to develop strong locking action, full commercial bolt tension, flexibility for locking action within the range of reasonable wrench torque, full length corners for wrench engagement and limited external side distortion to provide good wrench holding characteristics. 7

Having thus described our invention, what is claimed 1. A self-locking nut usable from either end of a coacting thread part and adapted to be tightened against an opposing flat surface, said nut comprising, in combination, a hexagonal nut body having substantially flat side faces intersecting at corners and like end surfaces in opposed relationship to one another, said nut body having a threaded central opening extending axially between the end surfaces and which is normally free running on the coacting threaded part, said end surfaces each being substantially symmetrical in contours and structure on opposite sides of a central plane passing through the centers of opposed side faces and axially of the nut body, said end surfaces having recesses of like size and concavely curved section and narrower than the diameter of said threaded central opening extending thereacross in opposed relationship to one another to provide a fiexure region of reduced section across the mid-portion of the nut body in one direction, and. said end surfaces having surface portions on opposite sides of said recesses which are each substantially flat and which normally extend away from one another laterally of each of the recesses in obtuse angular relationship to one another and have mid-regions extending practically to opposed corners of the nut body, the angle between said flat surface portions of each end surface being between 168 and 172, so that initial contacts thereof against said flat opposing surface are only near said opposed corners of the nut body and the nut body is flexed sufiiciently to take a permanent set at said flexure region when said flat surface portions bottom against the flat opposing surface when the nut is tightened and thereby limit the flexure of the nut body to a predetermined amount.

2. A self-locking nut as defined in claim 1, and wherein said threaded opening extends diametrically thereof into substantial portions of said substantially flat surface portions of the endsurfaces of the nut body, whereby substantial portions of the flat surface portions are both inside and outside of opposed maximum diameter limits of the threaded central opening so that when bottomed against the opposing surface they cannot tilt beyond such bottomed position when tightening force is applied.

3. A self-locking nut as defined in claim 1, and wherein the ratio of the maximum thickness of the nut body and the minimum distance between said recesses in the flexure region is between 2% and 2%.

4. A double ended self-locking nut adapted to have either end tightened against an opposing flat surface and comprising, in combination, a nut body having substantially flat side faces intersecting at corners andlike end surfaces in opposed relationship to one another, said nut body having a threaded central opening extending axially between the end surfaces, said end surfaces having like recesses of concavely curved section and narrower than the diameter of said threaded opening extending thereacross in opposed and aligned relationship to one another at the mid-regions of opposed side faces toprovide a flexure region of reduced section across the mid-portion of the nut body, and said end surfaces having portions extending outwardly from opposite sides of said recesses which are substantially flat and extend to the side surfaces of the nut body with the angle between said fiat surface portions at each end of the nut body being less than a straight angle by approximately 8 to 12, so that initial engagement of said end surface portions with the said opposing fiat surface is only at opposite outer extremities of said flat surface portions and at positions spaced laterally of said recesses, and said nut body being flexed at said flexure region when tightened against said opposing fiat surface until-said fiat surface only portions bottom against the opposing flat surface to limit flexure of the nut body to a predetermined amount and provide for the building up of holding pressure.

5. A double ended self-locking nut adapted to have either end tightened against an opposing .flat surface and comprising, in combination, a nut body having substantially flat side faces intersecting at corners and like end surfaces in opposed relationship to one another, said nut body having a threaded central opening extending axially between the end surfaces, and end surfaces having like recesses of concavely curved section and narrower than the diameter of said threaded opening extending thereacross, in opposed and aligned relationship to one another at the mid-regions of opposed side faces to provide a fiexure region of reduced section across the mid-portion of the nut body, and said end surfaces having portions extending outwardly from opposite sides of said recess which are substantially flat and extend to the side surface of the nut body with the angle between said flat surface portions at each end of the nut body being somewhat less than a straight angle, so that initial engagement of said end surface portions with the said opposing flat surface is only at opposite outer extremities of the flat surface portions and at positions spaced laterally of said the minimum thickness between said recesses being between one-third and one-half of the overall thickness, and the normal angularity of each flat surface portion with respect to a straight angle being between approximately 4 and 6.

6. A self-locking nut which is usable from either end, which turns freely on a co-acting threaded part until it engages an opposing flat surface and which is adapted to be tightened against the opposing flat surface, said nut comprising, in combination, a hexagonal nut body having substantially flat side faces intersecting at corners and end surfaces in opposed relationship to one another, said nut body having a threaded central opening therethrough which extends axially between the end surfaces, the opposite ends of said nut body having recesses of like size and contours therein which are symmetrical with respect to a central plane through the nut body and extend laterally of the nut body from the threaded opening substantially to two of said side faces which are opposed to one another, and said end surfaces having portions on opposite sides of said recesses which extend from said threaded central opening and said recesses practically to opposite corners of the nut body and to flat side faces of the nut body adjacent said opposite corners and are each substantially fiat throughout their extent and which are angularly related to one another so that the angle between the said portions of each end surface is less than a straight angle by approximately 8 to 12, each of said end surfaces being disposed to effect fiexure of the nut body between said recesses while it is being tightened and to bottom against said opposing flat surfaces to limit the flexure of the nut body to a value affording good locking action and a permanent set of the nut body in the flexed position.

7. A self-locking nut as defined in claim 6, and wherein the positions of maximum thickness of the nut body are at the regions of opposed corners thereof, whereby only said regions seat first against the flat opposed surface.

References Cited by the Examiner UNITED STATES PATENTS 1,111,382 9/14 Hibbard 151-21 1,204,491 11/16 Roof 151-21 1,420,725 6/22 Mattson l5 l21 1,774,081 8/30 Burns 151-21 2,016,610 10/35 Moeller 32 FOREIGN PATENTS 30,796 3/85 Germany.

EDWARD C. ALLEN, Primary Examiner. 

1. A SELF-LOCKING NUT USABLE FROM EITHER END OF A COACTING THREAD PART AND ADAPTED TO BE TIGHTENED AGAINST AN OPPOSING FLAT SURFACE, SAID NUT COMPRISING, INCOMBINATION, A HEXAGONAL NUT BODY HAVING SUBSTANTIALLY FLAT SIDE FACES INTERSECTING AT CORNERS AND LIKE END SURFACES IN OPPOSED RELATIONSHIP TO ONE ANOTHER, SAID NUT BODY HAVING A THEREADED CENTRAL OPENING EXTENDING AXIALLY BETWEEN THE END SURFACES AND WHICH IS NORMALLY FREE RUNNING ON THE COACTING THREADED PART, SAID END SURFACES EACH BEING SUBSTANTIALLY SYMMETRICAL IN CONTOURS AND STRUCTURE ON OPPOSITE SIDES OF A CENTRAL PLANE PASSING THROUGH THE CENTERS OF OPPOSED SIDE FACES AND AXIALLY OF THE NUT BODY, SAID END SURFACES HAVING RECESSES OF LIKE SIZE AND CONCAVELY CURED SECTION AND NARROWER THAN THE DIAMETER OF SAID THREADED CENTRAL OPENING EXTENDING THEREACROSS IN OPPOSED RELATIONSHIP TO ONE ANOTHER TO PROVIDE A FLEXURE REGION OF REDUCED SECTION ACROSS THE MID-PORTION OF THE NUT BODY IN ONE DIRECTION, AND SAID END SURFACES HAVING SURFACE PORTIONS ON OPPOSITE SIDES OF SAID RECESSES WHICH ARE EACH SUBSTANTIALLY FLAT AND WHICH NORMALLY EXTEND AWAY FROM ONE ANOTHER LATERALLY OF EACH OF THE RECESSES IN OBTUSE ANGULAR RELATIONSHIP TO ONE ANOTHER AND HAVE MID-REGIONS EXTENDING PRACTICALLY TO OPPOSED CORNERS OF THE NUT BODY, THE ANGLE BETWEEN SAID FLAT SURFACE PORTIONS OF EACH END SURFACE BEING BETWEEN 168* AND 172*, SO THAT INITIAL CONTACTS THEREOF AGAINS SAID FLAT OPPOSING SURFACE ARE ONLY NEAR SAID OPPOSIED CORNERS OF THE NUT BODY AND THE NUT BODY IS FLEXED SUFFICIENTLY TO TAKE A PERMANENT SET AT SAID FLEXURE REGION WHEN SAID FLAT SURFACE PORTIONS BOTTOM AGAINST THE FLAT OPPOSING SURFACE WHEN THE NUT IS TIGHTEND AND THEREBY LIMIT THE FLEXURE OF THE NUT BODY TO A PREDETERMINED AMOUNT. 